Recent apparatuses for operating a small water gate are of various types such as,
A) a type in which threads are cut on an operating rod, and a female screw fitted on the operating rod is turned by a drive mechanism, by which the operating rod is moved upward or downward, PA1 B) a type in which an operating rod is formed into a rack formed integrally by two steel bars having a rectangular cross section and a large number of pins connecting these two steel bars to each other, and a gear engaging with the rack is turned by a drive mechanism, by which the operating rod is moved upward or downward, and PA1 C) a type in which an operating rod is connected to a piston of a reciprocating hydraulic jack, and the sucking and discharging operations of hydraulic oil are performed, by which the operating rod is moved upward or downward. Therefore, various kinds of apparatuses have been put to practical use. PA1 a) The mechanism is complicated and expensive. PA1 b) The check and maintenance are difficult to do and require high cost. PA1 c) Fats and oils contaminate the environment.
However, these types of conventional apparatuses for operating a water gate not only are complicated in structure and high in equipment cost but also require much time and cost in daily check, lubrication, etc., which leads to a heavy burden on the installer.
Also, lubricating oil and hydraulic oil on a screw face and at parts of the mechanism drop into the water and contaminate the environment, which causes a bad reputation for the inhabitants of the neighborhood.
Further, the hydraulic jack type of item C) has a drawback in that the hydraulic jack becomes extremely expensive with an increase in the travel distance of operating rod.
In addition, when a door is lowered by gravity for the need of control, a further complicated mechanism must be added to perform speed control, which presents a problem of higher equipment cost.
The present invention has been made to solve the above problems with the conventional apparatus. Accordingly, an object thereof is to provide an apparatus for operating a water gate, in which air, which is inexpensive and has no fear of contaminating the environment, is used. Moreover, an operating rod is driven by the pressure of the air sent into air bags not by a conventional mechanism of air jack, so that it is possible to simplify the construction of the apparatus greatly.